Triquark-diquark models of a Θ(1540)?

Abstract

The enhancement in the flavour exotic NK channel seen by a number of experiments has been interpreted as a resonant pentaquark state, the Θ+(1540). Theoretical efforts to understand its structure, with the aim of explaining both the low mass and small decay width, have thrown up the possibility of a triquark-diquark P-wave correlation. We will discuss the constituent quark model study of Karliner and Lipkin and suggest that their P-wave excitation energy is an underestimate, a more plausible value raising the Θ mass in this model to more than 1700 MeV. We also propose on rather general grounds that these correlated quark models give rise to not only exotic baryon states, but also exotic meson states, in particular the strangeness +2, isoscalar ϑ+ which will decay to K+K0.